The present invention relates to testing of wireless RF devices under test (DUTs), and in particular, to controlling uses of multiple wireless points of access in a testing environment to manage loading by the DUTs during testing.
Many of today's electronic devices use wireless signal technologies for both connectivity and communications purposes. Because wireless devices transmit and receive electromagnetic energy, and because two or more wireless devices have the potential of interfering with the operations of one another by virtue of their signal frequencies and power spectral densities, these devices and their wireless signal technologies must adhere to various wireless signal technology standard specifications.
When designing such wireless devices, engineers take extra care to ensure that such devices will meet or exceed each of their included wireless signal technology prescribed standard-based specifications. Furthermore, when these devices are later being manufactured in quantity, they are tested to ensure that manufacturing defects will not cause improper operation, including their adherence to the included wireless signal technology standard-based specifications.
Testing of such wireless devices typically involves testing of the receiving and transmitting subsystems of the device under test (DUT). The testing system will send a prescribed sequence of test data packet signals to a DUT, e.g., using different frequencies, power levels, and/or signal modulation techniques to determine if the DUT receiving subsystem is operating properly. Similarly, the DUT will send test data packet signals at a variety of frequencies, power levels, and/or modulation techniques for reception and processing by the testing system to determine if the DUT transmitting subsystem is operating properly.
For testing these devices following their manufacture and assembly, current wireless device test systems typically employ testing systems having various subsystems for providing test signals to each device under test (DUT) and analyzing signals received from each DUT. Some systems (often referred to as “testers”) include, at least, one or more sources of test signals (e.g., in the form of a vector signal generator, or “VSG”) for providing the source signals to be transmitted to the DUT, and one or more receivers (e.g., in the form of a vector signal analyzer, or “VSA”) for analyzing signals produced by the DUT. Together, the VSG and VSA (as well as any internal or otherwise associated control software and/or firmware) establish one or more points of access (PoA) since they provide, to the DUT, access to the signal generating and analyzing resources of the VSG and VSA, respectively, via the applicable signal frequencies, communication channels, data packet structures, signal modulation types, etc., in accordance with the type of DUT being tested. (As is well known, a PoA may be more specifically referred to by different names depending upon the type of wireless system. For example, while in a Wi-Fi system it is generally referred to as a channel, in a mobile telephone system, such as cellular, the wireless point of access may more generally be referred to as a “cell”. For purposes of the present discussion, a PoA is a subsystem for enabling wireless signal connections and/or communications between a DUT and a tester.) The production of test signals by the VSG and signal analysis performed by the VSA are generally programmable (e.g., through use of an internal programmable controller or an external programmable controller such as a personal computer) so as to allow each to be used for testing a variety of devices for adherence to a variety of wireless signal technology standards with differing frequency ranges, bandwidths and signal modulation characteristics.
Referring to FIG. 1, a typical testing environment 10a includes a tester 12 and a DUT 16, with test data packet signals 21t and DUT data packet signals 21d exchanged as RF signals conveyed between the tester 12 and DUT 16 via a conductive signal path 20a, typically in the form of co-axial RF cable 20c and RF signal connectors 20tc, 20dc. As noted above, the tester typically includes a signal source 14g (e.g., a VSG) and a signal analyzer 14a (e.g., a VSA). The tester 12 and DUT 16 may also include preloaded information regarding predetermined test sequences, typically embodied in firmware 14f within the tester 12 and firmware 18f within the DUT 16. The testing details within this firmware 14f, 18f about the predetermined test flows typically require some form of explicit synchronization between the tester 12 and DUT 16, typically via the data packet signals 21t, 21d. Alternatively, testing may be controlled by a controller 30 which may be integral to the tester 12 or external (e.g., a programmed personal computer) as depicted here. The controller 30 may communicate with the DUT 16 via one or more signal paths (e.g., Ethernet cabling, etc.) 31d to convey commands and data. If external to the tester 12, the controller 30 may further communicate with the tester 12 via one or more additional signal paths (e.g., Ethernet cabling, etc.) 31t to convey additional commands and data.
Ordinarily when testing a wireless device (e.g., mobile telephony (such a cellular telephone handsets), wireless fidelity (Wi-Fi), Bluetooth, Zigbee, Z-Wave, or similar devices) with a tester, once communications between tester and DUT have been established, the tester and DUT will execute a test flow during which the tester or controller may control the behavior of the DUT (e.g., by executing control commands via driver software associated with the DUT). Commands may include instructing the DUT to receive test packets from the tester, or to transmit packets to the tester. The characteristics of the packets may also be controlled, such as signal frequency(ies), power level, data rate, modulation, etc.
Referring to FIG. 2, an alternative testing environment 10b uses a wireless signal path 20b via which the test data packet signals 21t and DUT data packet signals 21d may be communicated via respective antenna systems 20ta, 20da of the tester 12 and DUT 16. This type of test environment is often referred to as an over-the-air (OTA) test environment. Generally, at least for final production testing, an OTA test environment is preferred so that the DUT may be tested in its complete and final form so that not only the internal circuit subsystems are exercised but the antenna subsystem(s) of the DUT are exercised as well so that signal effects due to all DUT subsystems can be monitored and measured.
Test instrumentation in an OTA test environment is capable of handling multiple DUTs (e.g., 32 DUTs with 8 DUTs per point of access (PoA)). A DUT may enter the system at random and connect to any active PoA since in such OTA test environments with multiple tester points of access (i.e., transceiver subsystems) the user/tester does not have deterministic control of how or where a DUT autonomously connects to the test system(s). For example, when a test system(s) is broadcasting via multiple PoAs on different frequencies, a DUT may autonomously attach on any of these PoAs. When multiple DUTs connect randomly to different PoAs, test system resources are not assigned in an ideal manner. Conventionally, an external application has been required to detect the random resource assignments and then individually determine appropriate assignments and re-assign certain DUTs to one or more other PoAs. Such re-assignments require use of special redirection or handover procedures to establish a steady state loading of DUTs to PoAs before starting the tests. For example, such handover procedures in cellular telephony must support direction to and/or from LTE FDD/TDD and WCDMA, which requires an intelligent external test application for controlling the system to execute the relevant redirection or handover procedures. Hence, it would be desirable to be able to deterministically assign system resources and configurations of the test system, such as the PoAs, to each DUT without any action on the part of the DUT required or need for an external test application.